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n.
(in dentistry) a strap that is fixed round the back of the head and/or the neck and attached to an orthodontic appliance to aid tooth movement. It is normally worn at night and for part of the day.
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head·gear (hedґgēr) a harnesslike device fitting over the top and back of the head, serving as a source of resistance for extraoral anchorage for an orthodontic appliance. Called also headcap.Medical dictionary. 2011.